Gas turbine system



Sept. 7, 1937.

A. LYSHOLM GAS TURBINE SYSTEM Filed Feb. 23, 1935 3 Sheets-Sheet l Sept.7, 1937. A. LYsHoLM GAS TURBINE SYSTEM Filed Feb. 25, 1935 3Sheets-Sheet 2 INVENTOR. @fw

Sept. 7, 1937.

A.LYSHOLM GAS TURBINE SYSTEM Filed Feb. 23, 1935 3 Sheets-Sheet 3 j@ATTORNEY.

Patented Sept. 7, 1937 GAS TURBINE SYSTEM Alf Lysholm, Stockholm,Sweden, assignor to Aktiebolaget Milo, Stockholm, Sweden, a corporationof Sweden Application February 23, 1935, Serial No. 7,693

In Germany February 24, 1934 12 Claims.

'I'he present invention relates to gas turbine systems of the continuouscombustion type, sometimes referred to as constant pressure systems incontradistinctlon to intermittent or explosion type systems.

In the attempts to develop a practical continuous combustion system theprincipal diillculty has been to prevent failure of the turbine bladesdue to the high temperature of the motive lluid without reducing theinitial temperature of the motive iluid to a degree such that thepossible thermal eillclency of the system is too low to make itpractical.

Until recently it was thought that the problem of the continuouscombustion gas turbine system could be solved only by using initial gastemperatures so high that known materials available for turbine bladingcould not withstand such temperatures. Recently it has been foundpossible to evolve a practically operable gas turbine system by theutilization of double rotation radial llow turbines'of high eiclencyoperating with gases the-initial temperature of which is in the rangeoi.' from approximately 800 C absolute to 1000 C. absolute. Thissolution, however, has certain definite limitations when the radial flowturbine alone is employed. This is due primarily to the fact that therelatively very small area for llow of motive fluid at the inlet to theblading of this type of turbine precludes its economical utilization inmany instances where large volumes of motive fluid must be handled. In'gas turbine systems, the volume of motive fluid necessary to eiect agiven heat input into the sys/tem is very much larger than the volume ofsteam in a steam plant of corresponding heat input. This is because thespeciilc heat of internal combustion gases is less than the specificheat of steam. Consequently the development of a continuous combustiongas turbine presents a problem involving the handling of large volumesof motive lluid in a plant of given size. There thus arises the problemas to whether or not it is possible to use the axial flow 'type ofturbine in a system of this character, since the axial flow turbine isbetter adapted to handle large volumes of motive fluid than is theradial ilow type of turbine. However, because of inherent structurallimitations the axial ilow turbine will necessarily have such highlosses if operated in any manner that is practical with temperaturessuch as those above mentioned as being used with the radial flowturbine, that the turbine eillciency will be too low to give anacceptable overall thermal eillciency for the system. Consequently, ithas heretofore been generally believed that the axial ilow turbine isgenerally unsuitable for this type of system.

In accordance with the present invention, however, the axial flowturbine, with its desirable characteristic of ability to handle largevolumes of motive fluid, is employed, and the method of operation ol'the system and the means whereby such method may be carried into eiect,will now be explained.

It is known that modern types of axial llow turbines can be successfullyoperated with motive uid having an inlet temperature of as high as 540C., and that with such turbines at average inlet pressures of 15atmospheres there will be obtained comparatively high thermo-dynamicefllciency which may be as high as 86% or even higher.

I propose to utilize this type oi turbine which, v

if eillciency of the above order is to be obtained, must be of themultiple stage type, and which is preferably of the multiple stagereaction type, and to use this turbine with gaseous motive fluid theinitial temperature of which is within the range of which the upperlimit is approximately 540 C. It would appear, if the teachings of theprior art were accepted, that such utilization of this type of turbinewould be obviously unsuccessful because of the low initial temperature,but I have discovered that a practical system giving acceptable overallthermal emciency can be provided by utilizing this type of turbine,operating with gaseous motive fluid at this relatively low initialtemperature, provided that it is possible to recover by regeneration asuillcient quantity oi heat from the motive iluid as exhausted from thesystem and to return this recovered heat to the motive fluid in a mannersuch that it can be effectively utilized.

In order 'to effect the regeneration necessary to make my proposedmethod of operation successful, it is necessary to maintain the pressureof the motive fluid as admitted to the turbine at a relatively lowvalue. The reason for this is that if the initial pressure of the motivefluid is relatively high the amount of the heat drop in the motive fluidpassing through the turbine is so great that the exhaust temperature isnot suiliciently high for my purposes. In fact, in cases of high initialpressures it is even possible that the exhaust temperature will be solow that regeneration is impossible because of the fact that the exhausttemperature is below the temperature of the air when the latter iscompressed to the initial temperature of the motive iluld. Because ofthis circumstance, I propose, in accordance withlmy invention, toutilize for expansion in an axial flow turbine of the characterdescribed, motive iiuid the initial temperature of which is within arange not exceeding approximately 540 C. and having an initial pressurewithin a range of which the lower limit is approximately two atmospheresand the upper limit of which may be approximately six to eightatmospheres. For this range of pressures a radial flow turbine would berelatively undesirable because of the fact that with gaseous motiveiiuid comprising gases of combustion the specific volume of the gases istoo great to be most effectively handled by the radial flow turbine.When operating a turbine with an initial pressure as low as thatcontemplated in the arrangement above mentioned and with the turbineexhausting at not less than substantially atmospheric pressure, whichmust be the case when uncondensable gases constitute the motive fluid,the heat drop of the motive iiuid in the turbine is comparatively solittle that high exhaust temperature is a necessary result.V With higheX- haust temperature, a very considerable amount of regeneration may beeffected, and I propose, in accordance with my invention, to utilizeregeneration to return to the compressed air which constitutes one ofthe constituents of the motive iiuid, an amount of heat which is atleast as much and which may be more than the heat equivalent of the workextracted from the motive fluid in the turbine or turbines from whichthe exhaust gases are derived.

When the system is constructed in accordance with my invention, it ispossible, by means of regeneration, to add as much heat energy to theair by regeneration as is added by the combustion of fuel with the air,which fuel is injected or otherwise supplied to convert the compressedair into gaseous motive fluid. The necessity for such extreme use ofregeneration requires comparatively very large heat exchange apparatuswhich, moreover, should be constructed with particular care so as toafford high heat transfer efficiency. Such apparatus involves a veryconsiderable additional expense in the construction of the system, butthe additional expense required for this equipment is more than made upfor by the high operating efciency and the relatively low rate of fuelconsumption for the whole system when operating in accordance with theinvention.

While for the sake of simplicity I have described the aboveconsideration as applying to a system in which the initial pressure ofthemotiveA fluid for the entire system is within the comparatively lowpressure range mentioned, it is to be understood that the invention isnot applicable solely to low pressure systems, but is equally applicableto systems in which a plurality of turbines operating at differentpressure ranges are employed, and in which systems the invention isapplicable to the turbine or turbines operating in the lowest pressurerange in the system. Such turbines may conveniently be called endturbines.

As will hereinafter be more fully explained, high pressure turbineswhich may be of the radial flow type or of the axial flow type may beconnected in series with such end turbine or turbines, but regardless ofthe character of such high pressure turbine or turbines, thecharacteristics of the regeneration and of the initial temperature andpressure of the motive fluid as admitted to the end turbine or turbines,remain in substantially the same relationship when the invention isadhered to. Stated in another way, the amount of heat transferred to thecompressed air lby means of regeneration is at least as much or may bemore than the heat equivalent of the Work extracted from the motivefluid in the end turbine or turbines.

I further propose, in accordance with my invention, to so design thesystem that the overall thermal efficiency of the system attains itsmaximum value at part load,lwhich is preferably in the range of from 50to 75% of the normal full load for which the system is designed tooperate. The reason for this will later be more fully explained.

In order to more fully explain the nature of the invention and themanner in which it is carried into eiect, I have shown in theaccompanying drawings certain thermal diagrams and also suitableembodiments of apparatus for carrying the invention into eiect, which Iwill now proceed to describe.

Fig. 1 is a diagram showing certain efficiency characteristics of a gasturbine system embodying the invention;

Fig. 2 is another diagram illustrating other characteristics of such asystem;

Fig. la is a temperature entropy diagram illustrating a thermal cycletypical of one embodiment of a system embodying the invention;

Fig. 2a. is another temperature entropy diagram illustrating the thermalcycle of another embodiment;

Fig. 3 is a more or less diagrammatic plan view, partly in section, of agas turbine system embodying the invention;

Fig. 4 is a section taken on the line 4-4 of Fig. 3;

Fig. 5 is a more or less diagrammatic plan vieW of a system embodyingthe invention and having a separate double rotation radial iiow turbineacting as a high pressure turbine and exhausting to the portion of theplant with which the present invention is particularly concerned andFig. 6 is another more or less diagrammatic plan view of a thirdembodiment similar to that shown in Fig. 5, but utilizing a diierenttype of high pressure turbine.

In the diagrams of Figs. 1 and 2, I have shown certain characteristiccurves illustrating the conditions which will obtain in gas turbinesystems constructed in accordance with the present invention.

Fig. 1 refers to a gas turbine system of the type illustrated in Fig. 6-and the thermal cycle' of which is shown in Fig. la. The ordinatesrepresent percent thermal eciency `or usefull power output of thesystem, as the case may be, and the abscissae represent initial pressureof the motive uid, the initial pressure being considered as the pressureat the inlet of the end turbine or turbines of the system. Curve Iindicates thermal eiiciency of the system, and curve II indicates theuseful power output in kilowatts per kilogram air compressed in thecompressor means. The curves shown are based on calculated data assumingmotive uid temperature at the inlet of the turbine of 540 C., athermal-dynamic turbine elciency of 90%, compressor efficiency(isothermic) of 70%, regenerator eiiiciency of 92%, and a temperature ofthe compressed air leaving the compressor of 60 C.

I'his diagram shows that with increase of turbine inlet pressure theuseful power output per kilogram compressed air of the lsystemincreases, but that with conditions of the nature assumed the total oroverall thermal eiciency is very much more favorable in the field ofrelatively very low initial pressure than in the field of highpressures.

'nils is due, in part, to the nature of the utilization of heat by theregenerator under varying capacity conditions.

Fig. Zillustrates conditions obtaining in a turbine system such asillustrated in Fig. 3, the thermal cycle of'which is represented in Fig.2a. In this diagram the abscissae represent percentage of load, and theordinates represent thermal eftlclency, temperature of motive fluid,number of revolutions of the compressor in percentage of normal fullspeed or volume of compressed air in percentage of normal volume at fullload, as the case may be. In this diagram, curve III represents thethermal eiilciency, curve IV the temperature of the motive iluid at theturbine inlet, curve'V the temperature of the motive fluid as 'exhaustedfrom the turbine, or exhaust gas temperature, curve VI the speed of thecompressor, and curve VII the volume of air compressed. From thesecurves it will be evident that with increasing load on the system thespeed of the compressor and the volume of air compressed both increase,but that at the same time the temperature of the motive fluid asexhausted from the turbine decreases. In this connection, it is to benoted that in the range of very light loads, approaching idling load,curves III, IV and V are shown with both full line and dotted lineportions. 'I'he dotted line continuation of curves IV and V indicatesthe rapid rise of exhaust and inlet temperatures which accompany suchlight load operation if no control is provided to take care of this.These temperatures in many instances exceed safe values. In the curvesillustrated, the no-load exhaust temperature would be nearly 500 C., andthis temperature is too high for the exhaust end of the turbine bladesystem. Consequently, control is preferably provided whereby exhausttemperature at light load may be limited to a predetermined maximumvalue, and the solid line portions of curves IV and V indicate theconditions existing when such control is employed. A control of thisnature is not germane to the present invention and has therefore notbeen illustrated in this application. Such control is fully disclosedand claimed in and forms the subject matter of my copending applicationSerial No. 749,006, iiled October 19. 1934. The solid line portion ofcurve III indicates the effect on the overall efficiency` of the systemdue to the employment of such exhaust temperature limiting control.Increasing load, however, means reduction in regenerator efilciency dueto increase in quantity of air and decrease in the exhaust gastemperature.

It is also characteristic of heat exchangers of the type employed forregenerators that the efciency of heat transfer increases as the loaddecreases from a valve representing capacity operation of theregenerator to a value representing partial capacity operation.

'I'he curves shown in Fig. 2 are based upon a turbine inlet pressure offour atmospheres and with a temperature of motive fluid at the inletwhich is in the range of from 410 C. to 540 C. As will be seen fromthese curves, the emciency curve is comparatively at throughout themajor range of operation of the system with the maximum eillciency lyingwithin the range of 40 to of full load. With the above pressure andtemperature at the inlet of the turbine, it will be seen that the natureof the characteristics of operation of the units of the system providesan overall thermal etliciency, under the assumed conditions, which is ofacceptably high value throughout the major portion of the operating loadrange of the system.

'Iurning now to Fig. 3, the system shown therein is of the kind in whichthe turbines which separately drive the useful power means and the aircompressor are connected in parallel with respect to the ilow of motivefluid through the turbines, and in which these turbines, which are endturbines in the sense 1n which I employ this term, are also the highestpressure turbines in the system. In other words, in this system there isbut one pressure range of expansion of the motive fluid, as will be seenfrom the thermal cycle represented in Fig. 2a which will be referred tolater on.

In the system illustrated, I0 indicates an axial flow multiple stage gasturbine which is preferably provided with blading of the reaction type,and which preferably is constructed to afford full admission of motivefluid to the inlet of the turbine blading from a central admissionchamber i2. Rotor I4 of the turbine is connected to the rotor I6 of aircompressor IB, which is preferably of the multiple stage centrifugal orrotary type. Turbine 20, which advantageously is similar in constructionto the turbine I0, has its rotor 22 connected to the rotor 24 of agenerator 26, which delivers the useful power produced by the system.

'I'he invention is not limited to the use of an electrical generator fordelivering the useful power from the system. For convenience, I willrefer to turbine I0 as a compressor turbine and to turbine 2li as auseful power turbine.

Air is drawn into compressor I8 through the inlet 2l and is delivered incompressed state to conduit 30 connected to the regenerator indicatedgenerally at I2. From the regenerator the air is delivered by means ofconduit 34 to the combustion chamber 36, to which liquid or othersuitable fuel is supplied through fuel nozzle 38. Conduits 4ll and 42supply heated gaseous motive fluid, produced by the combustion of fuelin chamber 36, to the admission chamber i2 of turbine |0 and theadmission chamber 2i of turbine 20 respectively, the flow of motivefluid being in parallel to the turbines. I'he exhaust conduit 44 ofturbine i0 and the exhaust conduit 46 of turbine 20 lead to theregenerator 32, and from the regenerator exhaust gases are ilnallydischarged through conduit 48.

The specific design of the regenerator may be varied widely within thescope of the present invention. For purposes of illustration I haveshown more or less diagrammatically a regenerator of the recuperativetype in which a plurality of tubes 5U are disposed across the path offlow of the exhaust gases in their passage from conduits 44 and 46 tothe discharge conduit 48. The conduit 30 delivers compressed air fromthe compressor and is connected to a header chamber 52 communicatingwith one end of a part of the tubes 50. A header chamber 54 providescommunication between the air delivery conduit 34 and one end of theremaining tubes, and the opposite ends of all of the tubes are incommunication with a common reversing header or chamber 56.

The flow of air and motive fluid through the system will be more or-less evident from the drawings. Assuming the system to be in operation,air is drawn into the compresser and delivered in compressed state tothe regenerator, passing in two passes through the tubes 50 andreceiving heat from the exhaust vgases passing through the passage intothe regenerator through which the tubes 50 extend. The heated compressedair is then delivered to the combustion chamber, where combustion of thefuel admitted to the chamber further increases the temperature andprovides heated motive fluid which is delivered to the turbines. 'Iheexhaust gasesfrom the turbines passing through the regenerator deliver asubstantial part of their heat to the air passing from the compressor tothe combustion chamber.

As previously pointed out, the specific form of construction of theregenerator may vary within the scope of the invention, but in order tomake proper use of the invention the capacity of the regenerator must besutllciently great so that when any given system is operating underconditions productive of maximum thermal eiliciency for the system theregenerator will transfer from the exhaust gases of the system to theair at least as much heat as the heat represented by the heat drop ofthe motive iluid in the turbines, Stated in another way, the capacity ofthe` regenerator must be such that at least as much heat is added to thecompressed air by regeneration as is represented by the heat equivalentof the Work done by the motive fluid in expansion in the turbine. Thiscapacity may, of course, be readily calculated for any given design ofregenerator, since the exhaust temperature of the gases may bedetermined by calculation under the conditions of operation which areproductive of maximum efficiency of the system, and the temperature ofthe air delivered to the regenerator may also be determined for anygiven design of compressor.

Numerous different specific methods of controlling operation of thesystem in accordance with variations in load may be employed within thescope of the invention. Since, in accordance with the present invention,the inlet temperature of the motive fluid to the end turbines ismaintained at a relatively low value, some means for automaticallylimiting this temperature may advantageously be employed, and forpurposes of illustration and by way of example I have indicated in thecombustion chamber 36 a thermostatic element 58 arranged to operate avalve 60 in fuel line 62 so as to throttle the fuel supply if themaximum permissible value of the temperature of the motive fluid isexceeded. Variations in load on the system are, in a system of thischaracter, most advantageously taken care of by means of control of thefuel supply, and the control may advantageously be made responsive toload by means of a suitable governor 63 driven from the shaft of theuseful power turbine and controlling a main fuel supply valve 66 so asto reduce the amount of fuel supplied to the combustion chamber upon areduction in load on the system. It will be obvious that otherrefinements of control may be added, and that the system may becontrolled by manual operation of such controls as are provided.

As heretofore mentioned, the end turbine or turbines with which thepresent invention is primarily concerned need not constitute the entireturbine structure of the system.

In Fig. 5 I have illustrated by way of example a turbine system which isadapted to operate with expansion of motive fluid in a plurality ofpressure stages or, in other words, with a high Y pressure expansionstage ahead of the expansion stage represented by the end turbines. Inthis system the end turbines Il! and 2|! drive respectively a compressorI8 and generator 26, and exhaust respectively through conduits 44 and 46to the regenerator 32. As in the embodiment shown in Fig. 3, theseturbines are connected in parallel by means of conduits 40 and 42 foradmission of motive fluid from combustion chamber 36a. In this instance,however, a high pressure turbine 10 of the double rotation radial ilowtype is employed in addition to the end turbines. Turbine 10 comprisesoppositely rotating shafts ,12 and 14, shaft 12 driving the rotor of acompressor 16, the inlet of which is connected by means of conduit 18with the outlet of compressor I8. 'I'he outlet of compressor 16 isconnected by conduit 80 with the inlet of compressor 82, the latterbeing driven by shaft 14 of turbine 10 and having its outlet connectedby means of conduit 84 with the regenerator 32. Compressed air fromregenerator 32 is conducted by means of conduit 86 to combustion chamber36, to which fuel is supplied through pipe 62 under the control of acontrol valve 64 which may be manually controlled or which may begovernor controlled from the useful power turbine as shown in Fig. 3.From combustion chamber 36 the motive uid generated in this chamber isdelivered to turbine 10 and this turbine exhausts through conduit 88 tothe combustion chamber 36a. Fuel is supplied to the combustion chamber36a through pipe 62a, and the maximum temperature of the motive fluiddelivered from chamber 36a may be controlled by means of a thermostat58a controlling a valve 60a.

The operation of a system of this kind will be largely evident from thepreceding description of the system shown in Fig. 3. The low pressureend of the system operates in substantially the same manner as thatdescribed. 'I'he difference in the two systems is that by means of thecompressors 16 and 82 connected in series with compressor i8, the air iscompressed to a higher pressure than where a single compressor is used,and the motive fluid at this higher pressure which is generated in thecombustion chamber 36 is first partially expanded in the double rotationradial flow turbine 10, which drives compressors 16 and 82. Because ofthe higher pressure of the motive uid, the volume to be handled in thehigh pres- `sure expansion stage is less than would be the case with arelatively low'initial pressure, and for this reason the radial flowturbine may advantageously be employed.

Also, if desired, the radial flow turbine enables motive fluid to beutilized having a higher initial temperature than would be practical foruse in an axial flow turbine. Consequently, with this arrangement,advantage may be taken of higher pressure and temperaturecharacteristics of the motive fluid. The motive fluid exhausted atreduced pressure and temperature from turbine 10 is conducted to thecombustion chamber 36a, which, in this embodiment, acts as a reheater.Reheating of the motive fluid in this combustion chamber may be effectedin known manner by combustion of additional fuel with excess airremaining in the motive fluid as delivered from the primary combustionchamber 36. As in the case Where no high pressure turbine stage isemployed,

the temperature of the motive fluid leaving the combustion chamber 36ais limited to a relatively low temperature and the pressure is also lowso that the heat drop in the end turbines is comparatively small, withresulting high exhaust temperature, thus permitting the large amount ofheat recovery by regeneration which takes v place in the regenerator 32.

In Fig. 6, still another embodiment is illus trated, which is similar inarrangement to that lust described in connection with Fig. 5, the onlydifference being that instead of utilizing as the high pressure turbinea double rotation radial iiow turbine, an axial now turbine 00 of thesame general type as turbines It and 20 is employed. Turbine 90, in thisinstance, operates a compressor l2 connected in sexies by means ofconduits 1I and 34 between the low pressure compressor I l and theregenerator 32. In this arrangement, the axial ilow turbine 90 isutilized as the high messure turbine of the system, but when a turbineof this sortis employed instead of the radial flow type of turbine itwill be evident that because of operating characteristics which I havepreviously discussed, the initial temperature of the motive fluid asdelivered from the primary combustion chamber 36 must be maintained at arelatively low value, that is. within the range of which the maximum isapproximately 540 C.

'Ihe embodiments shown in Figs. 5 and 6 have been illustrated primarilyonly for the purpose of indicating that the present invention is notconfined solely to low pressure systems. It will be understood by thoseskilled in the art that the invention may be incorporated in manydifferent specific designs of systems intended to operate with aplurality of different ranges of expansion in different turbines, andthat the type, number and arrangement of the turbines of higher pressurein such systems may vary without affecting the principles of theinvetion.

In order to further illustrate the character of the thermal cycle in asystem such as that shown in Fig. 6, I have shown in Fig. 1a this cyclein a temperature entropy diagram in which the ordinates are temperatureand the abscissae entropy. In this diagram point er represents thetemperature of the air as drawn in by the compressor and the constantpressure line a represents the portion of the cycle during which heat isadded to the air, point a1 representing the temperature of the air asdelivered from the high pressure compressor, the point az representingthe temperature of the air as delivered from the regenerator, and thepoint a: representing the temperature of the motive fluid as deliveredfrom the combustion chamber. Line b represents the expansion of themotive fluid in the high pressure turbine, line b' indicating thetheoretical perfect adiabatic expansion line, and the point b1representng the temperature of the motive fluid as exusted from the highpressure turbine. The constant pressure line c represents the additionof heat to the motive fluid in the reheater, point ci representing thetemperature of the reheated motive iiuid which, in this instance, issubstantially the same as the temperature at the inlet of the highpressure turbine. Line d represents the low pressure expansion stage inthe end turblues' to a temperature di, and that part of the constantpressure line e from d1 to e1 represents the drop in temperature of theexhaust gases in the regenerator which eiects the heating of the airalong line a from the point a1 to the point as.

As will be seen from the diagram represented in Fig. la, the amount ofheat transferred by the regenerator to the compressed air is more thanthe heat equivalent of the work done by the motive uid in expanding inthe end turbines, the first-named amount of heat corresponding to line afrom point ai to point as, and the last-named amount' of heatcorresponding to line d from point ci to point d1. It will further beevident that in this instance the amount of heat added by regenerationand corresponding to line ai-ai is also more than the heat added bycombustion corresponding to line :zz-as.

In Fig. 2a, I'have illustrated the thermal cycle of a system of the kindshown in Fig. 3, in which there is but one expansion stage. In thisdiagram, the constant pressure line a from point a1 to point a2corresponds to the heat added to the air in the regenerator and the sameline from point a: to point as corresponds to the heat added to the airin the combustion chamber. Line b represents the expansion in theturbines a temperature at point bi, and the constant pressure line cfrom point b1 to point c1 represents the heat drop of the exhaust gasesin the regenerator.

By way of example, I give below the principal characteristics of theapparatus for a gas turbine system of the kind shown in Fig. 3 andembodying the principles of my invention. For such a system having afull load capacity of 2200 kilowatts, the compressor is preferablydesigned to deliver 20 kilograms of air per second at 4 kilograms persquare centimeter pressure, and at a temperature of approximately 60 C.Such compressor is advantageously designed to operate at full capacityat a speed of 3000 R. P. M., the compressor turbine advantageouslycomprising six rows or stages of blading and being adapted to operate at3000 R. P. M. The turbines are designed for an inlet temperature ofapproximately 540 C. at full load, the path for ow of motive fluidthrough the turbines being so designed that the turbines expand underfull load operating conditions approximately 20.2 kilograms of motiveiiuid per second from a pressure of 4 kilograms per square centimeter toan exhaust pressure oi' 1 kilogram per square centimeter, and from theinlet temperature to an exhaust temperature of approximately 320 C. Iheregenerator has a heat transfer surface oi' 1100 square meters capableof transferring from the above mentioned quantity' of exhaust gasessumcient heat to raise the temperature of the air delivered by thecompressor from its compressor outlet temperature of 60 C. to atemperature oi! 300 C.

While in compliance with the patent statutes, I have described myinvention in connection with certain illustrative examples of apparatusfor carrying it into effect, it will be understood that the invention isequally applicable to many dinerent variations of continuous combustiongas turbine systems in which the number and disposition of the severalturbines of the system may be quite different.

'I'he invention is accordingly to be understood as embracing all formsof apparatus and variations in method of operation falling within thescope of the appended claims, which are to be construed as broadly as isconsistent with the state of the prior art. l

Certain features oi construction relating to the turbo-compressor andturbo-generator units shown but not claimed herein are claimed in mycopending application, Serial No. 140,639 iiled May 4, 1937.

What I claim is:

1. A gas turbine system of the continuous combustion type having endturbine means and a regenerator, said end turbine means being of theaxial iiow type and having a plurality of expansion stages, meansincluding a compressor for supplying heated gaseous motive uid to saidturbine -means at a pressure not exceeding approximately 8 kg. per sq.cm., and means for conducting the exhaust gas from said turbine means tosaid regenerator to heat the air compressed by said compressor, saidregenerator having a capacity enabling it to transfer to said air anamount of heat equal to at least the heat equivalent of the work done bysaid motive fluid in expanding in said turbine means.

2. A gas turbine system of the continuous combustion type having endturbine means and a regenerator, said end turbine means being of theaxial iiow type and having a plurality of expansion stages, meansincluding a compressor for supplying heated gaseous motive fluid to saidturbine means, means for limiting the temperature of said gaseous motivefluid as admitted to said turbine means to within a range of which theupper limit is approximately 540 C., and means for conducting theexhaust gas from said turbine means to said regenerator to heat the aircompressed by said compressor, said regenerator having a capacityenabling it to transfer to said air an amount of heat equal to at leastthe heat equivalent of the work done by the motive fiuid in expanding insaid turbine means.

3. A gas turbine system of the continuous combustion type having endturbine means and a regenerator, said end turbine means being of theaxial ow type and having a plurality of expansion stages, meansincluding a compressor for supplying heated gaseous motive fluid to saidturbine means at a pressure not exceeding approximately 8 kg. per sq.cm., means for limiting the temperature of said gaseous motive iiuid asadmitted to said turbine means to within a range ofwhich the upper limitis approximately 540 C., and means for conducting the exhaust gas fromsaid turbine means to said regenerator to heat the air compressed bysaid compressor, said regenerator having a. capacity enabling it totransfer to said air an amount of heat equal to at least the heatequivalent of the work done by the motive fluid in expanding in saidturbine means. 4. A gas turbine system of the continuous combustion typehaving end turbine means, means including a compressor for supplyingheated gaseous motive fluid, means for supplying said motive uid to saidend turbine means at a pressure not exceeding approximately 8 kg. persq. cm., a regenerator for heating the air compressed by saidcompressor, means for conducting to said regenerator the exhaust gasfrom said end turbine means, said regenerator having a capacity enablingit to transfer to said air an amount of heat equal to at least the heatequivalent of the work done by the motive ud in expanding in said endturbine means, and said system being constructed and arranged to operateat maximum efiiciency at part load.

5. In the operation of a gas turbine system of the continuous combustiontype having end turbine means of the axial ow multiple stage type and aregenerator, that improvement which consists in forming motive fiuid bycompressing air and burning fuel therewith, expanding said motive iiuidin said turbine, conducting the exhaust gas from said end turbine meansto the regenerator, limiting the temperature of the motive uid at theinlet of said end turbine means to a relatively low temperature,limiting the pressure of the motive :duid at the inlet end of said endturbine means to a relatively low pressure, and adding to saidcompressed air in said regenerator an amount of heat equal to at leastthe amount of heat represented by the heat drop of the motive iiuid dueto its expansion in said end turbine means. i

6. In the operation of a gas turbine system of the continuous combustiontype having end tur bine means of the axial flow multiple stage type anda regenerator, that improvement which consists in forming motive iiuidby compressing air and burning fuel therewith, expanding said motivefluid in said turbine, conducting the exhaust gas from said end turbinemeans to the regenerator, conducting the motive uid to said end turbinemeans at a pressure not exceeding approximately 8 kg. per sq. cm., andadding to said compressed air in saidregenerator an amount of heat equalto at least the amount of heat represented by the heat drop of themotive iiuid due to its expansion in said end turbine means.

7. In the operation of a gas turbine system of the continuous combustiontype having end turbine means of the axial flow multiple stage type anda regenerator, that improvement which consists in forming motive uid bycompressing air and burning fuel therewith, expanding said motive iiuidin said turbine, conducting the exhaust gas from said end turbine meansto the regenerator, limiting the temperature of the motive fluid at theinlet of said end turbine means to a value not exceeding approximately540 C., limiting the pressure of the motive fluid at the inlet end ofsaid end turbine means to a value not exceeding approximately 8 kg. persq. cm. whereby to obtain a relatively low heat drop of the motive fluidin said end turbine means, and adding to said compressed air in saidregenerator an amount i of heat equal to at least the amount of heatrepresented by the heat drop of the motive fluid due to its expansion insaid end turbine means.

8. In a gas turbine system of the continuous combustion type, endturbine means comprising a compressor turbine and a useful powerturbine, said turbines being of the axial fiow multiple stage type, acompressor driven by said compressor turbine, a combustion chamber, aregenerator, conduits connecting said combustion chamber, said turbinesand said regenerator for ow of motive iiuid from the combustion chamberin parallel through the turbines to the regenerator, and means includingsaid compressor, said regenerator and said combustion chamber forsupplying motive fiuid to said turbines, said regenerator having acapacity enabling it to transfer to the air compressed by saidcompressor an amount of heat equal to at least the heat equivalent ofthe work done by the motive uid in expanding in said turbines;

9. In a gas turbine system of the continuous combustion type, endturbine means comprising a compressor turbine and a useful powerturbine, said turbines being of the axial ow multiple stage type, acompressor driven by said compressor turbine, a combustion chamber, aregenerator, conduits connecting said combustion chamber, said turbinesand said regenerator for ow of motive iiuid from the combustion chamberin parallel through thc turbines to the regenerator, and means includingsaid compressor, said regenerator and said combustion chamber forsupplying motive fluid to said turbines at a pressure not exceedingapproximately 8 kg. per sq. cm. and at a temperature not exceedingapproximately 540 C., said regenerator having a capacity enabling it totransfer to the air compressed by said compressor an amount of heatequal to at least the heat equivalent of the work done by the motivefluid in expanding in said turbines.

10. In a gas turbine system of the continuous combustion type, endturbine means of the axial flow multiple stage type, means including anair compressor for supplying gaseous motive iiuid to said end turbinemeans at low pressure, and a regenerator receiving exhaust gas from saidend turbine means for heating air delivered by said compressor, saidregenerator having a capacity enabling it to transmit to the air atleast as much heat as the heat equivalent of the work done by the motiveuid in expanding in said end turbine means.

11. In the operation of a gas turbine system o! the continuouscombustion type, that improvement which consists in extracting work fromgaseous motive fluid in a low pressure end range of expansion, andadding to a constituent of the motive fluid by regeneration from theexaust gases from the system at least as much heat as that representedby the heat drop in the motive fluid in said range of expansion.

12. In the operation of a gas turbine system of the continuouscombustion type having end turbine means of the axial ow multiple stagetype and a regenerator, that improvement which consists in formingmotive fluid by compressing air with increase of temperature due tocompression and burning fuel with the compressed air, expanding saidmotive fluid reactively in said end turbine means, conducting theexhaust gas from said end turbine means to the regenerator, limiting thetemperature of the motive iiuid at the inlet of said end turbine meansto a value not exceeding approximately 540 C., limiting the pressure ofthe motive fluid at the inlet end of said end turbine means to a valuenot exceeding approximately 8 kg. per sq. cm., whereby to extract arelatively small proportion of the avallable heat of the motive uid insaid end turbine means and adding to said compressed air in saidregenerator an amount of heat equal to at least the amount of heatextracted from said motive fluid due to expansion thereof in said endturbine means.

ALF LYSHOIM

